152 



THE AGE OF MAMMALS 



with (listinetly American affinities. Plesiocalhartes is related to the tropical 

 American king vulture {Sarcorhaniphus) ; Ortfwcnemiis approaches the Bra- 

 zilian chaha {Chauna chavaria); Elaphrocnemus approaches the 'quadruped 

 bird,' or hoatzin, of Central America, and Filholornis, the penelopes (Pe- 

 nclopiniie), likewise of Central and South America. The striking relationship 

 that exists between certain birds of the phosphorites and living American 

 forms justifies the assumption that there were intcrmigrations of New 

 World types during the Eocene or Oligocene. 



Eocene birds of North America and Europe. — It is interesting at this 

 point to refer to the little that is known of Eocene birds of North America. "^ 

 Of the Lower Eocene the Diairyma gigantea of the Wasatch of New Mexico 



bj pti 111 1 ri ( 1 [lie L '5 t.eological burvey 



Fig. 53. — -Chief Middle Eocene Formations (horizontal lines). Bridger, C C, of south- 

 western Wyoming. Washakie, D, of south central Wyoming. 



is a large flightless bird, possibly related to the genus of the same name in 

 England and France. The various species of Aletornis described by Marsh 

 are l^elieved to be allied to the cranes. They vary from the size of the 

 killdeer plover to that of a flamingo. The owls {Bubo) and woodpeckers 

 (Uintornis) are also provisionally identified. The few records we possess 

 of the birds of undoubted Eocene age in England and France point in the 

 same manner to early differentiation of bird life. In the Lower Eocene, or 

 Sparnacian of northern France, Belgium, and England, the giant Gastornis 

 is abundant, an animal as large as an ostrich, not a true struthious type, 

 however, but presenting rather affinities to the wading and aquatic birds. 

 In the Lower Eocene, or Ypresian, of the Isle of Sheppey, small vultures 

 (Lithornis), kingfishers (Ha.lcyornis), sea gulls, and herons have been found. 

 From the Upper Eocene of Montmartre Cuvier recognized eleven distinct 

 species. Altogether there were representatives of the Accipitres, or birds of 

 prey, of the Passeres, or tree perchers, of the Picarise, including the wood- 



' American Ornithologists' Union (J. A. Allen, Editor), Check-List of North American 

 Birds, 3d and revised ed. New York, 1910. 



